After years of playing, I'm still not done. Quality, near endless RPG fun.
1) As an Aragonian (lizardman) tank mage. Blasted through the main quest line easily.
2) As an elven maiden, playing a special class that the game allowed me to invent. The class is called "Whisperer" and emphasized soundless combat and stealth. She never read scrolls, and excelled in alchemy to poison her arrows. Whenever possible she attacked from stealth and cover. She had a story arc (in my head at least) that had her starting as merciless and evil. She did the Dark Brotherhood (assassin), and Thieves Guild quests first.
Later she was converted to the light side and did the penitence required for the Nights of the Nine DLC and only then began the main quest.
3) As a dumb warrior Orc. He used little to no magic and beat down enemies with cudgels and his bare hands. This time I played through the Fighters Guild storyline first and then through all of the rest of the content. By the end of the game this Level 50 monster could paralyze with a single blow and most high level enemies were easily defeated because he would knock them down and beat on them, while they would rarely get in a blow.
4) Now I'm playing as a Galahad like swift mage. Only light armor and daggers and spells. I've just cleared the Mage Guild quest line.
I've left so much out, but I hope that this gives you a tiny idea of what can be done, and what you can do in this amazing game world.